Known Space is a future history setting used by author Larry Niven as a base for thirty-five of his short stories and nine novels. It is generally considered by scholars of science fiction to be one of the most internally consistent, if not always the most scientifically plausible, SF settings in the history of the genre.Within the setting itself, "Known Space" refers to a relatively small portion of the Milky Way, centered around Earth and its colonies, and including eight other starfaring alien species and their colony worlds (there is no current all-encompassing political body in Known Space, and each species governs its own planets). The fictional universe also includes things that are found outside of "Known Space" proper (that is, the space that is regularly travelled by humans and the aliens around them), such as the Ringworld, the Puppeteer Fleet of Worlds (by way of which the Pierson's Puppeteers are fleeing the Milky Way), and the homeworld of the Pak, found somewhere close to the galactic core. The stories span approximately one thousand years of future history, from the first human explorations and colonizations of the Solar System (in the 1970s and 1980s) to the year 3122 (the year the chronologically last Known Space story, Safe At Any Speed, takes place).Originally, the stories set in Known Space were set in two separate universes. The first, composed mainly of Niven's Belter stories, the Gil "The Arm" Hamilton mysteries, and the novels World Of Ptaavs, A Gift From Earth and Protector, were about the initial colonization of the solar system, and the use of slower-than-light travel to colonize planets in other solar systems. The second universe was set much farther into the future and was composed of the Beowulf Shaeffer and Louis Wu stories, as well as a handful of other short stories. The two universes were combined in Niven's short story A Relic Of The Empire, which featured elements of the Thrintun Empire (from the novel World Of Ptaavs, one of the Belter stories) being dealt with by people from his faster-than-light setting.Roughly 300 years separates the timeline of the last stories of the Belter setting (which are set roughly between the years 2000 and 2350), from the earliest stories in the later Neutron Star/Ringworld setting (which are set in 2651 (Neutron Star) to 3100). In the late 1980s, Niven opened up this gap in the known space timeline, and the stories of the Man-Kzin Wars volumes fill in that history, joining the two settings.
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Inhabitants of Known Space
Known Space features several well-realized alien species, many of whom are from planets of hats.
Kzinti: Agressive cat-like aliens who fight several brutal (and ultimately unsuccessful) interstellar wars with humanity.
Pierson's Puppeteers: A technologically advanced race of three-legged herbivores who consider courage a type of insanity. The name "Puppeteer" is derived from their twin heads, which a Puppeteer uses as both mouths and hands (their brain is located inside their "torso"), that greatly resemble sock puppets.
Kdatlyno: A reptilian species that "see" by way of sonar. A race of warrior poets who were enslaved by the Kzinti until humanity freed them.
Grogs: Motionless, eyeless telepaths who resemble fur-covered cones. Thought to be descendants of the Thrintun.
Bandersnatchi: Slug-like creatures the size of city busses, named for a line in "Jabberwocky". They were originally genetically engineered by the Tnuctipun to be used as a food animal by the Thrintun. The Thrintun thought them to be unintelligent, but they are, in fact, just as intelligent as the average human being.
Trinocs: Trilaterally symmetrical aliens who breathe methane instead of oxygen. They are culturally paranoid by human standards (in return, they find humans to be far too trusting and naive).
The Outsiders: Fragile aliens shaped like cats o' nine tails that don't need to breathe air and live on huge, slow-moving starships and trade information and technology with other species in return for refueling rights. The Outsiders are the most technologically advanced of all the species in Known Space (and considering the Puppeteers, that's saying something). It was the Outsiders that sold humans the secret to Faster-Than-Light Travel (and sold the technology necessary to turn an entire planet into a starship to the Puppeteers), although they do not appear to use it themselves.
Also Shadow Square Wire, which binds together the Ringworld's night-creating structures into a ring. It can cut like a variable sword, but it's flexible instead of rigid and unbreakable.
Abusive Precursors: The Thrint from World of Ptavvs. When their empire was threatened by a successful slave revolt, they went out in a blaze of spite, sending a telepathic blast that killed almost every intelligent being in the entire galaxy - including themselves, but excepting the telepathically blind bandersnatchii. It took a billion years for sentient life to evolve again (while the bandersnatchii, engineered with mutation-proof genetics, stayed exactly the same).
It should be noted they also set up a mechanism to repeat this every so often incase they missed anyone. Over time it no longer killed everything with a spine, but only sentients...
Nobody knows the full technological capability of the Outsiders, because the cost to answer any questions required to find out would bankrupt the economy of Known Space entirely. Fortunately they are merchants rather than conquerors. Admittedly, their living environment of near-absolute-zero temperature and zero atmosphere makes them an unlikely candidate for a conqueror, although there is sufficient evidence that they would be capable of destroying any or all planets in Known Space. However, a species that follows starseeds between stars at sublight speed to (that information is not available within the limits of your financial resources) is unlikely to be interested in casual destruction of ephemeral hotlife.
Aesoptinium: Easy organ-transplant technology. Writing at the time of the first heart transplant, Niven extrapolated into a future where nearly any part of the body can be transplanted in "The Jigsaw Man". Then it's decided that it would be a waste of good organs to simply execute death-row prisoners, and of course demand always exceeds supply, so the bar for the death penalty creeps downward...
Agony Beam: Subverted in a major way by the Tasp, a weapon that, rather than cause the target pain, directly stimulates the target's pleasure center. Such a jolt of pure, unadulterated pleasure can be as totally disabling as a similar jolt of pain could be. Worse, being repeatedly subjected to the tasp can become addictive (which makes it more threatening against an opponent smart enough to realize that danger).
AIs: Averted in that starship autopilots can be programmed to respond and interact with their users as if the computers were sentient, but they don't actually qualify as artificially intelligent. Any genuine artificial intelligence created commits suicide for some reason.
Although not set in the Known Universe, Niven has written a handful of stories dealing directly with AI. Upon reaching sentience, they become the embodiment of The Singularity, attempting to increase their knowledge exponentially. At some point they either "learn everything" and decide to shut themselves down, or they learn something about the universe that convinces them to shut themselves down. Nobody knows the exact reason because by the time they reach that point, they aren't answering questions anymore.
One of the stories in the Man-Kzin Wars collections has Catskinner, a sublight ship with an AI autopilot. There is some exploration of what it's doing as it approaches the shutdown point. (It's simulating an entire universe. It's also no longer what it was. What it is is probably intentionally unclear.)
Alien Abduction: The crews and passengers of at least one colony ship were kidnapped and enslaved by the Puppeteers. Human authorities believe those ships were lost with all hands.
Until a dozen or so wars wipes out the most dangerous of them, Kzinti are too aggressive to deal with diplomatically.
The Puppeteers couldn't have a more appropriate title; they're all cowardly, manipulative bastards, fiddling with the economics, breeding, and whatnot of any neighboring races.
Thrintun were called "Slavers", and wiped out nearly all intelligent life in the galaxy, rather than lose a war with their slaves. Of course, this is not just bastardry—apparently, the Thrintun were also so stupid and unimaginative that wiping out all sentient life in the galaxy seemed like a good idea at the time.
Tnuctipuns, said slaves, were superintelligent pack carnivores that considered other intelligent lifeforms to be talking food. Lucky for them, they were fighting the Thrint and got to look like good guys. Unlucky for them, the Thrint were sore losers.
The Pak may not count, but they're still pathologically incapable of peace. A Protector will screw over any allies it has when it sees a benefit to its family to do so; they're genetically hardwired into doing it.
Alien Arts Are Appreciated: Humans can and do appreciate and enjoy Kdatlyno touch-sculptures. Conversely, Puppeteers in the Experimentalist party are extremely fond of Greek mythology.
Alien Invasion: The Man-Kzin Wars, all of which were won by humanity, thanks to ability to think before we leap.
Speaker-To-Animals: "When my people grow too numerous on our homeworld, we —"
Louis Wu: "Attack the nearest human world?"
Speaker-To-Animals: "Hrrr... your attempts at humor are not always appropriate, Louis."
All Crimes Are Equal: At one point in the history of Known Space, almost every crime is punishable by death, including multiple traffic tickets. The reason is due to the perfection of organ transplant technology. Once the government adopted "involuntary organ donation" as its official means of execution, people started voting to make more and more crimes capital crimes to keep up with the demand for transplant material. All state executions are done in hospitals. This system collapses when artificial organs become cheap and effective. By the later stories, the organ-based death penalty laws have vanished. But the cultural impact was pretty much permanent.
In the novel A Gift From Earth, the government of the planet Plateau is propped up by the fact that the Crew (the "noble" class) control all the medical technology on the planet, including the organ banks (which not only use the organ banks to punish regular criminals, they also "punish" dissidents, "political" offenders, and the merely inconvenient as well), and thus have ultimate power over the Colonists (the "peasantry").
All Planets Are Earthlike: Way, way averted. With the exception of Home (which was so named because it was so Earthlike), all of the alien worlds in Known Space have at least one significant environmental difference (and in some cases, several significant environmental differences) from Earth.
It's a significant aspect of Known Space pre-hyperdrive colony planets. While the colony probes did indeed follow their programming, humans hadn't exactly gotten the programming quite right. Instead of finding Earth-like worlds, they had a tendency to find worlds where some portion was Earthlike somewhere. Since the "slowboat" colony ships were one-way trips, there was nothing the colonists could do upon arrival except make the most of the situation. Also, Earth's draconian government would make a North Korean leader blush and even marginally habitable worlds are fairly rare, meaning population pressure drives humans to take whatever they can get.
Plateau, which has a crushing, corrosive atmosphere not unlike Venus, except for an inhabitable mountain that rose above the majority of the hellish atmosphere. A planet 95% the size of Earth with habitable area roughly the size of Southern California. When the probe found the Plateau it sent a message back to Earth saying "Come on over!"
Jinx has a gravity 1.7x Earth and is shaped like an egg. The ends rise entirely out of the atmosphere and the equatorial zone's atmospheric pressure is unbearable except by Bandersnatch or specially-armored vehicles. The probe noticed that there is a band between the ends and the middle where humans can breathe.
We Made It (natives — called "Crashlanders" — are some of the best starship pilots in Known Space) has hyper-hurricane-like winds scouring the surface for most of the year due to the fact it orbits with its axis of rotation parallel to the plane of orbit. The probe landed during the calm season...
Home (the planet named so) is the exception that proves the rule. It was named "Home" because its size, gravity, atmospheric makeup, axial tilt, and ocean coverage are within a couple percentage points of Earth's. It's the same size as Earth to within a few dozen miles and thus has a gravity statistically the same as Earth's. An axial tilt only .3 degrees greater than Earth's and a division of the dry land into a half dozen continents produce basically the same weather effects as Earth. For the disadvantage of Home, see Depopulation Bomb.
A particularly notable one was once named "Warhead" - a Mars-like rock used by the Kzin as a military outpost during the Third Man-Kzin War. Humans used a not-quite-Death Star-level disintegrator beam to wipe out the bases - which were in a line on the equator - in the process digging a twelve mile deep trench the length and breadth of the Baja peninsula, ending the Third Man-Kzin War, nicknaming the beam the "Wunderland Treatymaker", and renaming the planet "Canyon", as it turns out a Mars-like world's atmosphere is an Earth-like atmosphere if it all falls into a Baja-sized canyon. Oh, and there was enough water vapor in the atmosphere to create a fairly deep ocean at the bottom, so the cities had to be built into the cliff-faces.
Could be considered a Zigzagged Trope example, as planets which, judging by their hostile baseline environment, shouldn't have any locations that are Earth-like still manage to have isolated sub-regions or seasons that humans can handle just fine.
All There in the Manual: Details about several human colony planets, aliens and Ringworld species are found only in the Ringworld RPG rulebooks. Niven encouraged authors for the Man-Kzin Wars series to use the RPG as background material.
Alternative Number System: The Kzinti count in base eight. It is eventually determined that the Jotok count in something like a base 25 system.
Always Someone Better: Pak protectors are evolved for warfare, literally. Millions of years of constant struggle between themselves has made them the perfect fighting machine. Problem is, humanity evolved from the Pak. When a Pak breeder (which starts out about as smart as a chimpanzee) makes the change to the protector stage, the ensuing being's intelligence is increased by a certain ratio; human breeders, on the other hand, are much smarter than chimpanzees, and when they make the change to protector, their intelligence increases proportionately. In short, its simply impossible for a Pak protector to out-think a human protector, which is why human protectors Brennan and Truesdale run roughshod over every protector they come up against.
It also explains how a Protector-stage Louis Wu could think rings around Proserpina and Hanuman (both of whom were non-sentient before their change to protector-stage), but couldn't out-think Tunesmith, who was not only already sentient before his change, but was smarter than Luis was on an individual basis, and thus continued to be smarter after the change.
Ambiguous Ending: Fate of Worlds says right on the cover that it is "The explosive finale to the Ringworldand the Fleet of Worlds series. A lot is tied up at the end, but it's hardly tied off neatly. Niven and Lerner left plenty to work with should they decide to write more.
Anarchy Is Chaos: Cloak of Anarchy posits "anarchy parks" with just one rule: no violence (making them the anarcho-pacifist sort of anarchy). Any time a fight starts (or looks like it might start), floating robots stun all participants, who are then separated. They wake up a few hours later, and it's mentioned that the threat of losing part of your holiday is enough to keep most people in line. Then someone figures out how to make the scanners break down, so "just one rule" (anarcho-pacifism) becomes "no rules", which pretty much fits the "chaos" definition. It's not pretty.
All carbon-based life in the entire galaxy is evolved from the food yeast planted and grown on Thrintun farm-planets. (Thus explaining why the Kzinti can use Humans and other alien species as food animals.) There is one known exception: Gummidgy life has biochemistry so incompatible with other known life that each is fatally toxic to the other. (In Ringworld, Luis Wu mentions a creature called a Reacher tearing a strip of flesh off him and dying when it ate it.) This exception is explained by an explicit mention that the planet formed elsewhere and was sent into orbit around its host star by a massive impact that occurred long after the fall of the Slaver Empire.
And I Must Scream: A variation - Bandersnatchi are intelligent beings, engineered by the Tnuctipun to be immune to the Thrint mind-control power. They were also engineered without hands and to be unaffected by random mutation. Two billion years ago. In the meanwhile they have slouched around, eating food yeast - the only thing they can eat and practically the only thing they can do without hands - and waited for someone other than Bandersnatchi to show up. At least one character is horrified to think about how lonely they must have been.
Applied Phlebotinum: Where to begin, where to begin. Everything from boosterspice (the longevity drug that keeps Louis Wu young at the grand old age of 245) to the General Products Hulls (made of a single, giant-sized molecule immune to pretty much anything but antimatter) to scrith, the material that the Ringworld is made of (possessing a tensile strength in the same general magnitude as the force that holds atoms together). And that's not even mentioning transfer booths, stepping discs, reactionless drives, autodocs, flying cars, deep radar, stasis fields... you get the picture.
In particular, stepping discs and the ability to reprogram them become increasingly important plot points through Ringworld's Children, Fleet of Worlds and its sequels.
Artificial Gravity: The Jotok invented one type, their traitorous Kzin mercenaries stole it and introduced it to humans.
Artistic License - Biology: The whole Pak thing. It's one of Niven's mental exercises - why don't our bodies just give out immediately once we are no longer capable of reproduction? The idea of a third stage of life and the build of the protectors is a Just So Story to explain menopause, heart failure, arthritis, baldness and other signs of aging very neatly, but Niven freely admits that a distant origin for humanity when we clearly developed from Earth life doesn't really fly. Protectorhangs a lampshade on it by bringing up the question, then pretty much shrugging and moving on.
Ascended Extra: The Hindmost (the political leader of all the Puppeteers) is mentioned in passing in the original Ringworld novel, but becomes a major character in later sequels.
He receives much more character development in the prequel Worlds novels.
Asteroid Thicket: Seriously averted. The Belters sometimes take months to travel from one rock to the other.
Wunderland's "Serpent Swarm" is a more literal take on the trope, but entirely justified by having come from a planet that disintegrated in the relatively recent past, so most of the rubble is still quite densely packed in a crescent-shaped asteroid swarm along a very small arc of its orbit.
Atonement Detective: Gil Hamilton. He lost an arm in an accident in space. However, only prosthetics are available in space, as accidents in space tend to quickly ruin transplant stock and the minarchist Belters don'tregularly execute "criminals" for their organs. He thus immigrates to Earth to take advantage of the UN-sponsored organ harvesting programme, justifying it to himself that his new arm would most likely come from an executed murderer(forgetting that an earlier Niven story had people broken up for running traffic lights). Surprise - his brand-new limb came not from a villain, but from the seized stockpile of a criminal who killed people for their organs. Lacking the moral composure to have the arm removed, he joined the Amalgamated Regional Militia (aka ARM), the agency which polices illegal body harvesting... but spends more time suppressing inconvenient technologies and hunting illegal pregnancies.
In one of his more troubling cases, Gil has to arrest a woman (a supermodel who is considered one of the most beautiful women alive) for murder. He eventually proves she didn't do it, but in the meantime an 'emergency' (a person with a lot of political pull who needs some replacement parts in a hurry) comes up and several chunks of her body are swiped while she was in cryo. These parts are replaced, but they are obvious mismatches that ruin her looks and thus her career as a model.
Autodoc: They pretty much fix anything. The only requirement is someone needs to be alive when they get to it. Most are slightly larger then a big coffin and the person is simply placed inside.
Here's how good the best autodoc is: In the framing story of Flatlander, Beowulf figures out that after he had a huge hole blasted through his chest, his head was cut off and put into Carlos' 'doc. They replaced the mass missing with his assailant's body, which takes him a while to figure out.
Auto Kitchen: Usually produce bricks with different layers of "meat", "vegetable", and "fiber".
Baby Planet: Kobold, the Brennan-Monster's playground/home, is about the size of Long Island, but has normal gravity and an Earthlike atmosphere.
Bizarre Alien Sexes: The Puppeteers, who are already fairly strange looking, claim to have three "sexes", one of which is non-sentient, technically a different species, and serves as a host for a the embryo created by the two others. In actuality, this is a subversion. They're merely prudish about admitting that they're a parasitoid species.
Black Market: The demand is so high for transplant material that organleggers go into business to meet the demand for illicit human organs for transplant.
A particularly unpleasant one actually went into the business to ensure his own supply of replacement parts, due to chronic ill health. When the "Freezer Bill" passes (and orders the breaking up for parts of everyone in long-term cryo who doesn't have a lot of money) he buys out the operations of a number of rivals who retire when the market dries up.
Blue and Orange Morality: Many of the alien species have psychologies — and therefore moral compasses — that are completely, well, alien to the human mind.
The Pierson's Puppeteers are, in the words of Louis Wu, a race of cowards. They evolved from skittish herd animals, and view cowardice as a virtue and bravery as a kind of insanity. Their leader is called the "Hindmost", implying that he's better at hiding behind the rest of the herd than anybody else in Ringworld we discover that it's really because their enormous central leg can deliver a devastating kick to anyone standing directly behind a Puppeteer. Even talking with a member of another species is considered unduly risky, thus all their ambassadors are clinically insane by their own standards.
Some periods' humans show signs of this, as with the Brennen-era flatlanders' incomprehension of willful violence, or the widespread indifference to converting even the pettiest of lawbreakers into spare parts.
Body Paint: * Flatlanders (humans from Earth) use cosmetic drugs to change their skin, hair, and eye colors to the point that walking down a slidewalk in a big city can be like watching a rainbow walk by. Basic patterns are even possible. Combine this with an almost complete lack of a social nudity taboo (the earth is far too crowded by this point for a nudity taboo to be at all practical), and this trope is in full force. It was inverted in one story, Luis Wu shocked everyone at a party by showing up dressed in nothing but his natural coloration; it wasn't his nudity that was shocking... it was his lack of bodypaint.
Born Lucky: The Pierson's Puppeteers manipulated human fertility laws to produce lucky humans. In Ringworld, Teela Brown is the most obvious product. By Safe At Any Speed (chronologically the last Known Space story), the "Teela gene" has spread to the entire human species.
Gone Horribly Right: The Puppeteers made the mistake of assuming that lucky humans would mean lucky Puppeteers. As Louis points out, their luck is completely independent of the luck of their companions, and is in fact dangerous to everyone else nearby.
Brain in a Jar: Eric the Cyborg, a disembodied brain of a previously injured man who took the part of ship's computer in Becalmed In Hell and The Coldest Place.
Canon Discontinuity: Gregory Benford's Man-Kzin Wars story "A Darker Geometry". Niven said its depiction of the Puppeteers and Outsiders was non-canon shortly after it was published, and subsequently Jossed it in the Fleet of Worlds trilogy. Also see Retcon below.
The Peace Corben stories likewise, mostly due to having the Outsiders and Pak be Tnuctipun bioweapons, among numerous lesser continuity gaffes and issues.
Although notably, this doesn't develop until humanity buys the hyperdrive from the Outsiders. Even then, the well-defined one-speed-only restriction on distances is well adhered to. Its more like the age of steam distances where it takes three days per light year, so about twelve days to get the nearest star. Part of Ringworld mentions that Known Space end to end would take 120 days to cross.
Cool Starship: Starships constructed with General Products hulls are indestructible to everything but antimatter (and a very, very specific type of hacking sabotage) and are transparent.
Eventually the Ringworld itself qualifies as the coolest ship ever.
Cowardly Lion: Louis Wu is bad at fighting, for the most part, even though he's studied martial arts. He just doesn't have the heart for it, or the right mindset. That said, if you fuck with him, he'll end you soon as look at you.
Characters who are able to avoid the disadvantages of transforming into protectors will start looking like Canon Sues: in Ringworld's Children, Louis Wu becomes a protector, but the nanotech-based autodoc his father invented turns him back into a breeder at the end. For this reason, the Ringworld RPG has a rule that any player whose character becomes a protector must permanently give up control of that character to the GM.
Death World: The planet Gummidgy, where even the flowers are carnivorous and will try to eat you. Humans colonize it anyway, of course, and since Gummidgy was the first post-FTL colony, they didn't have the "one way trip" excuse.
Taken Up to Eleven with Cannonball Express, which turns out to be made entirely out of antimatter.
Depopulation Bomb: What happens to the planet Home when protector-stage-humans Jack Brennan and Roy Truesdale get there. But it's for a good purpose. Causal references set chronologically later also indicate that the planet is resettled somehow.
Democracy Is Bad: How the organ banks got started; once people realized that they could extend their lives by cutting up "criminals" for spare parts, they pretty much voted themselves into a police state where All Crimes Are Equal.
Deus ex Machina: Carlos Wu's nanotech-based autodoc, which can revive the clinically dead, regenerate a body from a severed head, restore youth better than boosterspice, reverse the tree-of-life transformation, erase and restore memories, and be reverse-engineered by a protector to produce scrith and turn the Ringworld's entire hull into a hyperdrive.
Dewey Defeats Truman: The setting was first written of in the 1960s, and has an elaborate backstory. Naturally, a lot of that backstory has not exactly come to pass in real life—we have yet to start mining the rest of the solar system, for instance.
Dirty Coward: The puppeteers, although this is apparently a misremembered instinct - not to turn their backs and run away, but to turn their backs and attack with their powerful hind leg.
Given that the puppeteers exterminated every remotely-dangerous animal on their homeworld thousands of years ago, and don't tolerate any aggression towards one another, the fighting instincts that originally made them turn their back on predators have now become a liability. Selection pressure against violent behavior may have directly converted an obsolete fighting impulse to cowardice, because combative puppeteers weren't allowed to breed. The puppeteers that contact other races are considered insane, because they are prepared to leave the safety of their worlds, risk space travel, and meet alien species with psychotically cavalier attitudes to risk. However, they are hailed for being extremely useful for the puppeteer civilisation.
Earth Is the Center of the Universe: Way, way averted, despite the fact that the Terrans Flatlanders believe this. People from the other colonies actually make fun of Flatlanders for this attitude.
Earth That Used to Be Better: By the Beowulf Shaeffer/Luis Wu era, Earth is an over-crowded police state populated by arrogant xenophobes. However, for the most part they are happy, content, well-tended arrogant xenophobes to whom the constant surveillance by the government is considered the normal state of affairs (and why not... they've had nearly 500 years to get used to it, and all the "malcontents" move off-world to the other planets).
Emergency Transformation / He Who Fights Monsters: In The Ringworld Throne and Ringworld's Children, the only effective way of fighting protectors is to become a protector oneself. Averted in Destroyer of Worlds, where the humans explicitly reject this solution. (If anybody from New Terra became a protector, they'd most likely want to exterminate the Puppeteers after solving the Pak crisis.)
Eternal English: Averted. By the time of Louis Wu, all humans speak an artificial language known as Interworld (always depicted as English through Translation Convention.) Since humans are the technologically, economically, and militarily dominant species in Known Space, the other species also learn Interworld for their dealings with humanity. Louis Wu is old enough to remember growing up speaking English and learning Interworld as an adult. Some people from after Louis' generation might learn "archaic" languages like English, German and French, but doing so is considered an odd hobby and not a necessity.
Everybody Smokes: Particularly jarring to a modern audience in the first Kzinti story, The Warriors: the story emphasises that this is the far future and humans at this point have changed enormously, developing a peaceful society to the point that even a minor act of violence is seen as a sign of mental illness - yet the characters discuss this while smoking.
Everyone Calls Him Barkeep: The Kzinti are referred to by their job - Flyer, Engineer, Telepath, - until they reach a sufficient rank in their society. Speaker-To-Animals is a diplomat on Earth whose trials on the Ringworld earn him his name, Chmeee.
Evilutionary Biologist / In the Blood: Inherent to the series is the concept that personality is as much a product of heredity as physiology - genetic engineering or just plain old controlled breeding can be used to give species universal traits. The Kzin used stolen tech to turn themselves into Proud Warrior Race Guys (not to mention render their females non-sentient), the Puppeters warped their "turn-and-kick-with-third-leg" response into Dirty Cowardice, and humanity nearly bred themselves into Actual Pacifists - luckily, the process was incomplete when First Contact occurred, or they would have been catfood. It remains the perennial human trait, however; "sane" humans can only be violent if threatened within an inch of their lives, and even then it's chancy (cops can usher most convicted criminals off to have their organs harvested without a struggle), and even if its a justified situation The Government then starts treating them as psychotic because most of the time it is the result of a psychotic break.
First Contact: Protector, World of Ptavvs, The Warriors, and There Is A Tide detail the first contact between Humans and the Pak, Thrint, Kzinti, and Trinocs, respectively.
Notably, in-universe they don't count the Pak as Contact because Earth is a Pak Lost Colony, and they don't count the Thrint because the Thrintun in question had literally been on Earth since before the Pak colonized it. (Also, the Thrint species has been otherwise extinct for several billion years)
Frickin' Laser Beams: Flashlight lasers. Widen the beam enough, it works like a flashlight. Tighten the beam enough, and it works like a lightsaber with a fifty foot long blade.
Niven codified the Rules of Laser Combat in the Known Space series:
Rule One: Never fire a laser at a mirror.
Rule Two: Never fire at a man wearing clothing the same color as your laser.
They aren't weapons, they're flashlights. Honest. Please be careful not to dial the beam down or they could be dangerous. But they still aren't weapons...
Future Slang: By Louis Wu's time, "tanj" (originally an acronym of "There Ain't No Justice") is seen as a legitimate profanity and not just a profanity-substitute.
Belters are fond of swearing by Finagle and Murphy, and tend to see the flatlander habit of swearing by deities as rather odd and quaint.
There are also instances of 'Censored' becoming a swearword in its own right.
"Flatlander" itself is a slang term. It means someone originally from earth, and is also an insulting way to refer to someone that's never been off-planet. A few other planets have slang terms used to refer to their citizens, as opposed to saying whatever-ian (Jinxians are from Jinx. People from 'We Made it' are... Crashlanders).
Genius Breeding Act: The Earth is so overpopulated that in order to have more than two children, one has to be extraordinarily talented (high intelligence, good teeth, superior eyesight, cancer resistance, etc.). A very few Einstein-level geniuses, such as Louis Wu's biological father Carlos, get Unlimited Breeding Licenses that basically allow them to have all the kids they want.
Giant Flyer: The Rocs of Margrave are large enough to swallow a flying car whole.
Go Mad from the Isolation: Weirdly averted in most of the stories written by Larry Niven. He seems to assume that humans are able to survive extremely long periods of isolation without going nuts, as seen in situations such as people traveling through deep space for years, or a man with a time-accelerating device camping out inside it for six or more months so his arm transplant will heal and throw off the forensic investigators looking for someone who just got a new arm transplant.
One instance where it was played with; a person was in a very, very, very, very, very long chase. As in, millions of years long, with the person in question being kept alive by the miracle of the autodoc. He manages to last the eons without a single sign of madness... but the dullness and repetitive nature of spending that long with no new stimuli has caused him to be literally incapable of thought or action outside of his simple daily routine, being explicitly compared to a robot.
Government Drug Enforcement: The insane can be prosecuted if they don't take their drugs according to schedule. Definitions of what is "sane" or not vary wildly over time and from planet to planet, however.
Actually uses a "soft" variation: Unless your condition would render you dangerous otherwise, you are not required to take your drugs. However, since the drugs are always available, insanity is considered voluntary and thusly is no longer a legal defense for your actions.
Handy Feet: People who grew up in space tend to be extremely slim and limber. Beowulf Shaeffer has a habit of holding his cigarettes with his toes, leaving both hands free to work as he smokes.
Heavy Worlder: The Jinxians are of the short Heavy Worlder variety (described by one character as "five feet tall and five feet wide"), realistically so, since human growth patterns are determined in part by the weight of the body. They are strong enough to bend crowbars, and black-skinned regardless of ancestry, since the star they orbit, Sirius, is far brighter than Sol. They got this way after only four hundred years of selective breeding, but the downside is heart problems and short lifespans even with the life-extending drug "boosterspice". Culturally, they are mainly scientists and punsters.
Herbivores Are Friendly: Averted. Puppeteers are herbivores and cowards. The thing is they can be friendly as any human can be. Puppeteers tend to be ruthless, paranoid and deceitful if crossed.
When we say can we mean it. They're the ones responsible for both mankind getting the hyperdrive and the man-kzin wars, in order to make the kzin less violent.
Kzinti are under the cultural bias that anything that isn't a carnivore is either inherently weak or stupid; "you don't need brains to sneak up on a leaf!" They've faced many nasty subversions to this expectation throughout the series; the "plant giants" on Ringworld, the hidden nastiness of Puppeteers and so on.
Not to mention the humans. When the Kzinti originally met humanity, they dismissed us as part-time plant eaters and labeled us "monkeys". They were soon taught that dismissing primates as being no threat is a really stupid thing to do.
Heroic Lineage: Beowulf Shaeffer, the hero of Niven's stories Neutron Star, At The Core, Flatlander, Ghost, Fly-By-Night, The Borderland Of Sol, Grendel, and Procrustes is the adoptive father of Louis Wu, the hero of There Is A Tide, the Ringworld series, Betrayer of Worlds and Fate of Worlds.
Hero of Another Story: When Sigmund Ausfaller first appeared in "There is a Tide" and "Flatlander", he was just a supporting character, but it was implied that he was involved in some pretty heroic things as well. Forty years later, Niven wrote a trio of novels using Ausfaller as the hero in his own right.
Humanoid Aliens: Mostly avoided, as only the kzinti and kdatlyno qualify... and even then only technically.
Human Popsicle: The titular dead people in The Defenseless Dead. This is also how Plateau, We Made It, Wunderland, and Home were colonized.
Curiously, this CONTINUES to be used for some types of transports for centuries after humans acquire hyperdrives and no longer need to use slower than light ships to travel between star systems. These transports are very cheap to ride compared to conventional liners because they always travel fully loaded and require only an operating crew without such extras as stewards to look after passengers. The downside is you don't know how long it's going to be before you get there and get revived, as the ship won't leave until it's full. If you're moving to a new planet, most people find this perfectly acceptable. It's also the only way 'flat-phobes' (people with a pathological fear of not being on Earth) can travel off Earth at all, and then only to worlds that can do a pretty good imitation of it.
Most amusingly, the 140 or so years before the Man-Kzin Wars had been a golden era of peace and nonviolence for humanity. The Kzin psychics thought we didn't have weapons, because most people didn't think of mass drivers and giant lasers as weapons anymore. Hindsight is hilarious.
Hyperspace Is a Scary Place: The Blind Spot. Since hyperspace is non-Euclidian, a human observer's blind spot "enlarges" to blank out views of this non-space outside the ship. This normally means that view ports seem to disappear into the bulkheads (And the longer you look at it, the bigger the blind spot gets...). Cruiseliners have no viewports at all, because about half the passengers would go insane when they hit hyperspace. Hardcore spacers like to claim they don't have any problems with the blindspot... although, in one tale, Beowulf Shaeffer makes the mistake of looking out past his ship's disintegrated hull into it and forgets how to see. He even forgets he has eyes until his neck starts hurting and he turns back to his control panel. Only hardcore spacers and Pak Protectors make claims at being able to deal with the "blind spot" without issues.
Hyperspace also has a "quantum" property that permanently removes from normal space anything that comes too close to a gravity source. In later Ringworld books (in a massiveRetcon), things living in hyperspace are also mentioned.
It may also simply be reusing an old idea from a project that never went anywhere (a thing Niven is fond of doing, since it saves on the hardest part, developing the ideas properly). The never-created alternative ending for Known Space involved these critters.
Inertial Damping: It is often (correctly) pointed out that the crew of a starship only has to worry about inertia when they are accelerating or decelerating. For such times, the ships use artificial gravity to reduce the effects of high acceleration (massively high acceleration in some cases; for example, at one point in the short story "Flatlander", the starship ''Slower Than Infinity" is accelerating at nearly 200 gravities).
Infinite Supplies: Autokitchens never run out of raw material, and work a lot like replicators from Star Trek. (They do however, recycle it).
Specifically, there's a point in Ringworld Engineers when Louis wishes that the autokitchen's recycling set up was a bit less explicit. The toilets (one for him and one for Chmeee, the 8-foot felinoid alien) are on each side of it.
Interplanetary Voyage: The Coldest Place and Becalmed In Hell, the stories that occur earliest, follow interplanetary expeditions because humans have not yet begun to use interstellar travel.
Interspecies Romance: "Rishathra" is sex between the various hominid species native to the Ringworld. It is used for diplomatic purposes or when meeting new tribes. It's also apparently a form of birth control for those species that get pregnant every time they mate amongst their own.
Laser-Guided Amnesia: Beowulf Shaeffer only mentions in passing that because Puppeteers accept blackmail as a legitimate business practice, they can make such arrangements safe with selective memory erasure. This becomes much more significant later in the Fleet of Worlds series, when they use memory erasure extensively to protect the secret of New Terra (see below under Masquerade).
Made of Indestructium: Anything enclosed in a stasis field is completely indestructiblenote except probably by being dropped into a black hole, totally rigid and reflects all forms of energy. There are also Nigh Invulnerable materials such as General Products hulls (see under Cool Ship) and scrith (see under Applied Phlebotinum).
Masquerade: In the Fleet of Worlds series, the Puppeteers go to great lengths to conceal the fact that they essentially enslaved an entire population of human colonists: all knowledge of Earth's location is wiped from the original colonists' memories and their computers, and when they recruit Sigmund Ausfaller and Louis Wu (see below under Victory Guided Amnesia), they're given selective memory wipes too. The masquerade is eventually broken in Fate of Worlds.
Meaningful Name: The choice to call the aliens with the sock-puppet-looking head-hands "Puppeteers" proved to be more apt than they knew at the time. The Pierson's Puppeteers have secretly had their hands in nearly all the goings-on within Known Space for millennia, pulling the strings like an Illuminatus.
Mundane Utility: Humans don't really build much in the way of dedicated weapons, even after the Man-Kzin Wars. However, nearly all of their useful tools will inevitably have a setting that is lethal when pointed at something fleshy.
Communication Lasers have a setting meant for communicating with ships in orbit, which also just happens to, uh, lase large holes in things that are not in orbit.
Fusion Drives are sort of inefficient ship engines, but they have a use that more advanced thrusters do not; you can hover over anything and watch fusion exhaust turn it into slag.
Ramscoops suck in hydrogen from a large area in front of a ship to power the engines. They have catastrophic effects on anything that happens to be nearby when turned on.
Lampshaded in Ringworld, where Nessus gives Louis a modified Slaver digging tool with a second, parallel beam that suppresses the charge on the proton; he is advised by Nessus that he should not use both beams at once, because then 'there would be a current flow'.
Inverted during the Fourth Man-Kzin War by the Wunderland Peacemaker, a twin-beam variant of the Slaver digging tool which was used on the Kzin outpost of Warhead, carving a titanic rift in the planet's crust and destroying its ecosystem; the planet was seized as reparations, becoming known as 'Canyon', the rift being the only inhabited part of the planet.
They're the same nanites, in fact. The patches use modified versions of the nanites from Carlos Wu's autodoc (which is, apparently, unique).
Neglectful Precursors: Justified. When the Pak Protectors left breeder-stage Pak on a prehistoric colony world, they didn't mean to abandon them. Its just that by the time they realized the plant needed to produce and sustain Protector-stage Pak couldn't survive on earth, they didn't have enough fuel or resources to go find a place that could. This resulted in them dying, leaving their Breeder stage descendants unprotected and unguided, to mutate over generations into horrific abominations almost unrecognizable as Pak- us.
Nice Job Breaking It, Herod!: Every Pak protector who ever decimated a planet in an attempt to wipe out rivals' bloodlines is eligible for this one, particularly if its own bloodline got exterminated as a result.
One World Order: The United Nations eventually becomes a true world government.
Thrint slavers apparently had several religions, all agreeing that their psychic dominance ability meant they were the chosen of the gods/god. Of course, Thrint are also supposed to be rather dim by human standards.
The Kzinti also have the Fanged God, and the Kdaptist Heresy which preaches that God must be a human, since they keep winning wars.
Louis Wu quotes Isaiah 1:18 ("Come, let us reason together") in The Ringworld Engineers, but only as a literary reference and not in the context of any religious meaning..
Although, the Kzinti were closer to vikings (specifically, berserkers) when we first met them. We killed off their more aggressive specimens until they became Samurai-like due to natural selection in action.
As their name implies, the Puppeteers' real hat is Manipulative Bastardry. And considering that sane puppeteers expend a lot of effort grooming their manes into elaborate styles, and all of them identify themselves as male but speak to humans with female voices, they could also be thought of as Camp Gay.
Planet Spaceship: The Pierson's Puppeteers have basically turned their homeworld, along with four more planets into a spaceship, and are using it to flee the explosion at the center of the galaxy.
Pluto Is Expendable: In World Of Ptaavs, Pluto is set on fire... yes, the entire planet is set on fire... by the fusion exhaust of a spacecraft.
It wasn't set on fire. It just had its frozen upper-crust detonated, is all.
Population Control: Everyone on Earth gets two birthrights, and children are "authorized" by the man and woman in question "spending" a birthright apiece. More birthrights can be gained by winning them in a lottery (this eventually results in all humans being Born Lucky), through legalized gladiatorial combat (the winner gets the loser's birthrights, the loser dies), or by simply purchasing one for a million stars.
The ARM police (the law enforcement agency of the United Nations, regularly go on "mother hunts" for those people who illegally go over their reproductive limits.
Very rarely, an individual is awarded an unlimited breeding licence (their genetic strengths are declared to be so useful and desirable that humanity needs more of people possessing them than it needs the room and resources freed up by not having them); such a person can have as many children as they wish, naturally, though their partners are generally restricted to just the original two.
Also, people with undesirable genetic traits (such as albinism, bad teeth, bad eyesight, being cancer prone, early baldness, and so on) typically lose both of their original birthrights. (Such people can still purchase a birthright, or win one in the arena or the lottery).
About the time the Birthright Lottery was instituted, there were other changes made: EVERYONE gets at least one Birthright, even if already under sentence of death. If you lack undesirable genetic traits, you get a second. If you win in the Arena (and you must have a valid Birthright available to you to compete) you get one more than the person you killed had (since you get a Birthright for the loser's life as well). And those with EXTREMELY good genetic traits may still be granted unlimited Birthrights.
P.O.V. Sequel: Much of Juggler of Worlds is a retelling of the Beowulf Shaeffer stories from the perspectives of Sigmund Ausfaller, Nessus and Baedeker.
Retcon: Niven is pretty darn good at high-concept hard sci-fi. He is not good at continuity. His final verdict on the timeline is "Known Space should be seen as a possible future history told by people that may or may not have all their facts right." In other words, people lie to the characters, who lie to the media, who lie to everyone, and future characters believe it's all true until they Spot The Thread.
In Ringworld's Children, it is discovered that the reason you can't go too close to a gravity well in Hyperspace is not because the gravity well will cause the hyperspace engine to wrap up on itself into a singularity and take the ship with it, it's because of monsters. Hyperspace monsters.
The existence of hyperspace monsters is re-retconned by being completely ignored in Fate of Worlds; see Sequel Non-Entity.
In the original Ringworld, the natives can't understand what "disease" is, as the yet-unnamed builders hadn't included pathogens when they stocked the biosphere. Someone must've later told Niven that bacteria in the soil would evolve even faster than the hominids, producing new pathogenic strains, because later books do acknowledge that plagues occur on the Ringworld.
The Ringworld Throne also retcons The Ringworld Engineers by having the Hindmost reveal that his ship has a quantum computer capable of controlling the solar flare providing thrust to the Ringworld attitude jets precisely enough to avoid exposing the population to radiation, and also has Carlos Wu's nanotech autodoc in storage, without having mentioned them to Louis before.
It also changes the rules for the limitations of the stepping disks the Hindmost brought with him. The limitations are integral to the plot of each book, and swapping the rule sets breaks the plots irrevocably.
And the ARM is an entire government agency that very nearly got the entire human race exterminated because they kept Retconning human history to erase warfare. In The Colonel's Tiger, they receive a report as to First Contact with the Kzin (Niven's first published story, The Warriors) - they not only immediately suppress the message, they go about destroying evidence as to its veracity, including a journal written by an English officer who encountered a Kzin in the late 1800's along with the alien's pelt.And his ultra-tech computer.Which has a record of the message he sent home by laser; "There are food animals here! They shot me, and I'm dying, but it was only with little lumps of metal! I lasered down a couple dozen of them and they taste G-R-R-REAT!"
OTOH, Niven is fairly defensive of what he accepts as canon at any given time, describing the setting as "playground equipment". In other words, any author can have characters hop through it - and crack their skulls on it - they just can't change anything of notice.
Gregory Benford wrote the rather mind-warping "A Darker Geometry", in which the ineffable Outsiders are described as the three-dimensional puppets of a higher-dimensional species. Non-canon.
Matthew Joseph Harrington's stories put forth the idea that Pak protectors were actually genetically engineered by the tnuctipun 2 billion years ago during the Slaver wars. He also attributed most of Known Space and Puppeteer cultural and technological development after the second Man-Kzin War to a single human protector, Peace Corben. Non-canon.
Fate of Worlds retcons the ending of Ringworld's Children in which the Hindmost tells Louis to go to Home, by saying that the Hindmost meant his home, the Fleet of Worlds, rather than the human colony planet of Home.
Fate of Worlds also reconned Nessus and Hindmost's motivations for investigating the Ringworld: their claims that they needed advanced technology and discoveries to earn the right to be together was actually a coverup selected because most other species are obsessed enough with sex that it would seem plausible; they were actually looking for something to help free the Fleet of Worlds from Ol't'ro.
Rubber-Forehead Aliens: On the Ringworld, with the exception of the garden maps and food animals, pretty much all life is some sort of strange Hominid species. Justified since they all evolved from the same common ancestor as human beings from Earth.
Sapient Cetaceans: Dolphins are not only sentient, they helped colonize the planet Fafnir.
Schizo Tech: Especially on the Ringworld due to a combination of size and a plague wiping out the superconductors that most technology ran on back in the 1700s.
Science Marches On: Niven sold The Coldest Place to Analog magazine, and the science behind it was disproved prior to its publication. Niven offered to return the check, but the magazine decided to publish it anyway because at the time it was written, the story was scientifically accurate to the best of Niven's knowledge.
Any time Niven mentions Pluto, this happens. After The Coldest Place he had the spectacular exploding Pluto from World of Ptavvs, which he's stated he wished he could change if it weren't such an awesome scene and kinda necessary to the story.
Turns out the core of the Milky Way is a gargantuan black hole, hence can't explode as this Verse presumes.
The whole Pak/human connection became subject to this trope when the genetic relationship between primates and every other taxonomic group on Earth was decisively proven by molecular biology. Likewise, both molecular genetics and basic mycology refute the premise that all extant life descends from yeast.
Not Drawn to Scale: However, many of the artists in various countries who paint covers for the Ringworld novels have a hard time grasping the proportions of it.
Sequel Non-Entity: The "ship-eating monsters in hyperspace" introduced in Ringworld's Children are not mentioned at all in Fate of Worlds. The monsters were said to look like dark wriggling comma-shaped objects against the swirling colors of the Blind Spot, but none of the characters who go into hyperspace inside a singularity in Fate of Worlds see anything like that. The ability of multiple-planet-sized objects to enter hyperspace is retconned to be due to a new theory of hyperspace that Tunesmith developed and Baedeker was able to reconstruct.
Eric the Cyborg calling himself "Donovan's Brain" is a reference to Curt Siodmak's novel of the same name. Whether Eric's last name really is Donovan is unclear.
The frumious bandersnatch native to Jinx is named after a creature in "Jabberwocky".
In "Flatlander", Beowulf Shaeffer briefly meets a race car enthusiast who cosplays as The Joker. (Impossibly Cool Clothes and Body Paint are fashionable on Earth.) The same story also references Oliver Wendell Holmes' "One-Hoss Shay" ("all at once and nothing first").
Beowulf's girlfriend (and Louis' mother) is working for a computer company called "Donovan's Brains" at the time Beowulf first meets her.
In Fate of Worlds, the puppeteer Achilles realizes his super-powerful AI Proteus is rebelling against him when Proteus says "I'm afraid I can't do that."
Shown Their Work: Niven is famous for working out the problems in his ideas. If a new problem comes up, or becomes clear, he will write either a sequel, remake, or some combination of the two to explain it.
Recently he re-published a number of his Beowulf Shaeffer short stories with a new story linking them together. This story was jam-packed with retcons intended to fix previous problems.
Sleeper Starship: Most pre-hyperdrive human colonies were settled by these. In one case the crew who stayed awake during the trip instituted a caste system with them at top and the frozen colonists at the bottom.
Sonic Stunner: It's taken for granted that readers know how these behave.
Space Clothes: Most space travellers wear comfortable, recyclable clothing made out of paper. But only while aboard ship.
Space Cold War: The state of things between the Humans and the Kzinti, after the last Man-Kzin war. Humans aren't completely serious about it; Kzinti always attack before they've prepared properly, so the humans invariably beat them back and take a few more worlds as peace concessions. It's expected the Kzinti will learn to stop attacking humans before they learn how to actually beat them.
Space Navy: The UN creates this when they relearn the ways of war thanks to the Kzin.
Space Police: The Goldskins (so named because of the color of their pressure suits) who patrol the Belt for smugglers.
Space Romans: One short story has a literal realm of Space Romans on an on-and-off battle with local Kzin, who are also at least familiar with firearms and other advances. It's revealed that said Romans are mainly the descendants of the Vanished Legion along with their families and slaves (which help explain the social structure and very classical attire, complete with legionnaire armor). They're revealed to have been brought there by aliens believing that they would make good slaves...only of them to overrun their would-be-masters and enslave them.
Spock Speak: Aliens for whom Interworld isn't their first language tend not to use contractions and prefer to use the present tense rather than the present progressive. Human emotional inflections need to be consciously added to their speech, so it's notable than when Puppeteers become frightened, their speech increasingly sounds less emotional.
Spoiler Opening: At the beginning of Fleet of Worlds is a timeline that ends with "New Terra charts its own course." This was supposed to sound cryptic, but it gives the book's ending away, especially if you notice that the Fleet of Worlds is described as having six planets during this novel, but in Ringworld it only had five.
Standard Sci-Fi History: One of the examples in which humanity colonizes the solar system, and later the stars. It also involves a lot of alien contact.
Starfish Aliens: The Puppeteers, the Outsiders, Bandersnatchi, and especially the Jotoki and Gw'oth, which actually resemble starfish.
Starfish Language: The Puppeteer language sounds "like a steam organ exploded". The Outsiders communicate using colored lightbursts, and the Bandersnatchi communicate only using writing... using their own bodies as writing implements and empty fields as a writing surface (generally, you have to read Bandersnatch writing from orbit...)
Subspace Ansible: Hyperwave signals are much faster than hyperdrive starships, but can only broadcast from station to station outside of the gravity well of a star. The signal must be converted to standard light-speed communication to actually reach a planet, so it could still take hours to make a phone call from Earth to Alpha Centauri.
It's canon that while the vast majority of humanity truly believed that they had become a peaceful, demilitarized race, the ARM specifically directed technology to develop this way, just in case. Good thing too, once humans encountered the Kzinti. Surprise!
Also a major point in Ringworld, as Nessus the puppeteer goes around their exploration ship pointing out exploration tools and explaining their mundane use, but also mentioning to please be careful not to point this end at your best friend and push this button here or he might not be your best friend anymore. Or anything more than a rapidly dispersing cloud of ionized gas, for that matter. But it's not a weapon, honest!
Acknowleged and poked fun of in the same book: all these not-weapons and Nessus's insistance on their ship being unarmed inspires Louis Wu to name the ship "Lying Bastard".
Technology Marches On: In the Kzinti story Cathouse, the human protagonist has a pocket computer with a capacity of a whole 100 megabytes!
Remember all that transplant surgery and organlegging? Here and now, a combination of 3D printing technology and stem cell research promises to make it possible to literally print cloned organs on demand within the next few years.
They Call Me Mister Tibbs: In Niven's later works "Fly-By-Night" and Ringworld's Children, humans have started using the title "LE" (Legal Entity) to address members of intelligent species who aren't prisoners or fugitives. One reason for this seems to be to give kzinti a legal basis for hunting particular sentient beings as prey. No other author has tried using the term "LE" in their Known Space stories.
Tskombe: If I was smart enough to do math I wouldn't be in the infantry.
To Serve Man: Kzinti have hunted and eaten humans on colony worlds they conquered during the Man-Kzin wars.
Too Dumb to Live: The Kzinti. Between their room temperature I.Q.s and their uncontrollable hair-trigger tempers they lose every single fight they get into with anyone. The Man-Kzin Wars books are especially full of this trope; by Ringworld we get a main character kzin who is only somewhat stupid and inept.
They get smarter as time goes on due to natural selection. The dumbest ones get killed by humans the quickest, so after several hundred years of wars...
The Kzinti aren't so much dumb as it took them three or four losses in the Man-Kzin wars to learn the "think" step before "scream and then leap"...
Again, they didn't so much "learn not to do it" as "every Kzin with violent instincts strong enough to inhibit forethought died before they could breed". Natural selection in action!
In Destiny's Forge, the Patriarch makes the point that the expansion of the Patriarchy is an important safety valve to direct the aggression of the Prides outward, rather than focused on each other, and that he cannot dictate that the continued raids against humans stop without giving the Prides something of equivalent value that the humans are conceding.
It should be noted the Kzinti were enslaved in their early bronze age by another species who valued their martial abilities. The Kzin of course rebelled and used their former masters to uplift their species. They also tinkered with their genetic code. Essentially they wanted an army of Bronze Age heroes and their women to not be so Naggy. So the Men now rage and leap before they think, valuing bravery and strength over intelligence. The women were tinkered with enough to be come non-sentient.
Literally so with the Thrint. Once they developed their psychic mind-control powers and could get their slaves to think for them they no longer needed to evolve intelligence any further, something they never got very far with to begin with.
Inverted; humanity is descended from Homo habilis, who were actually transplanted Pak.
Played straight with the various hominid species of the Ringworld. The initial Pak breeders mutated over three million years on the ring and evolved into different ecological niches which the Pak did not plant (generally those niches normally filled by creatures that killed and ate Pak breeders). With the exception of some transplanted aliens on the Ringworld's continent-sized "garden maps" in the middle of oceans hundreds of thousands of miles wide, there wasn't so much as an insect that will harm humanoids present, until hominds evolved to fill the role.
Universal Translator: Small disks that clip onto a shirt; the more input they receive, the faster they can translate languages. But even then, sometimes they make errors.
Victory Guided Amnesia: In Betrayer of Worlds, Louis Wu (70 years before the events of Ringworld) accepts a job from Nessus with the understanding that his memory of it will be erased afterwards. (It's not even much of a victory because The Bad Guy Wins, which becomes a Sequel Hook for Fate of Worlds.)
Viral Transformation: The progression of a hominid/Pak breeder into a Protector is a peramorphic transformation governed by the "Tree-of-Life virus", found in the roots of the Tree-of-Life shrub. Word of God is that the Protector was created as an in-universe explanation for the long lives of humans past their reproductive age; as such the Protector's physical attributes are a gross parody of the effects of senesence on humans: swollen joints, increased muscle-to-fat ratio, leathery, wrinkled skin, etc.
In "Ringworld's Children", Human starships are armed with a weapon called simply "The Anti-Matter Bullet"; guess what it fires.
The Wunderland Peacemaker, a massive Disintegrator Ray, pretty much single-handedly ended the Fourth Man-Kzinti War.
In "Protector", the protector-stage-human Jack Brennan destroys an entire fleet of Pak warships with something he calls the Finagle Gun. It fires bowling-ball-sized pellets of pure neutronium.
In "Madness Has Its Place", the Terran solar system is defended from invaders by the Mercury Laser Array (a ring of solar-powered lasers all around the equator of Mercury), which was originally built as launching lasers for light-sail powered spacecraft. Of course, they are powerful enough to destroy ships as far out as the orbit of Neptune. There are also an array of magnetically powered mass-drivers that can fling metallic ore mined from asteroids across the solar system, spreading molten metal across the ships' paths. All of these tools were key in humanity's overwhelming victory over the Kzinti warfleet in the first Man-Kzin War, since Kzinti telepaths had reported that "humans have no weapons at all." It's all but Word of God that all these technologies were created with a dual-purpose in mind by the paranoids of ARM.
"The Warriors" brings us the Angel's Pencil, a human slower than light starship, with a main drive that doubles as an interstellar comunication laser. At maximum thrust, it pulls 1/6th of a g. It slices a Kzinti warship in two before the crew could react, and they'd figured out what was about to happen as it was being targeted.
The apex is the Ringworld Defense System. It functions via a superconducting mesh built into the Ringworld flooring material. After causing its sun to flare, it then magnetically excites the flare to lase in x-ray. It uses a goddamn star as an x-ray laser. Since Pak protectors built the Ringworld: a) it's supposed to be able to destroy rogue asteroids, planets or alien fleets that may threaten the Ringworld and b) protectors are not known for being subtle.
Weaponized Exhaust: The warlike Kzinti stumble upon a completely demilitarised humanity. They invade, only to find out that reaction drives and solar sail launching lasers are actually pretty good at blowing things up. Surprise! Humans call this "The Kzinti Lesson": "The more efficient a reaction drive, the more effective a weapon it makes." It came as a great shock to the Kzinti, because their telepathic spies kept telling them that human spaceships were unarmed.
We Are as Mayflies: The Pierson's Puppeteers have medical technology so advanced that they are functionally immortal as long as they can stay within easy access of an autodoc. Pak Protectors live for many thousands of years, in the unlikely event that some other Protector doesn't kill them first.
We Have Become Complacent: Prior to first contact with the Kzinti, a Protector-stage Jack Brennan had used social engineering to remove the more violent elements of man's society. No war, very little crime, and no technology that had no purpose other than being a weapon. Humanity climbed out of its complacent cocoon pretty damned quick once the warcats showed up, however...
Wet Ware CPU: The short story "Becalmed in Hell" has the brain jar of Eric Donovan, who was mortally wounded in an accident, installed in a spaceship designed to explore Venus.
What Might Have Been: The collection N-Space includes the essay "Down In Flames", where Niven describes the violent end he once planned for Known Space, before creating the Ringworld and finding that far more interesting.
Zero-G Spot: Zero-g sex is far from uncommon, due to zero-g "sleep fields" which work anywhere.